There are three major sources for acids, which can cause tooth demineralization. The first source are the acids generated by cariogenic oral bacteria from food debris. These acids are carboxylic acids derived from the carbohydrates of the food debris that are metabolized by the oral bacteria. Such acids are rather weak, but act for extended periods on the teeth. The second source is the exogenous food acids that are present in the foodstuffs themselves, in particular in fruits, fruit juices or in artificial soft drinks, or in salad dressings. The third source are endogenous acids, in particular hydrochloric acid-containing gastric juice, which may come into contact with the teeth upon vomiting, such as in bulimia patients, or in reflux disease patients. These latter two types of acids are rather strong but act only for short times on the teeth. Tooth demineralisation caused by the latter two types of acids is termed “erosive tooth demineralisation” and is not related to cariogenic oral bacteria. Since acid-containing soft drinks have enjoyed a rising popularity among consumers in the past time the problem of erosive tooth demineralisation by food acids has become more acute, and a marked percentage of the overall population is nowadays afflicted by it. Similarly, a rising number of (mainly female) patients are subject to bulimia. Erosive tooth demineralisation is not noticed by the afflicted subject for quite a long time, and the pathological condition is thus often only diagnosed at a very late stage. Since erosive tooth demineralisation is considered irreversible (in contrast to tooth demineralization caused by cariogenic bacteria) it is essential that it be prevented from happening in the first place, or if it has already taken place, that it be prevented from proceeding further or that its progression be slowed down.
Fluorides are customarily used in oral care products such as toothpastes, dental gels or mouthrinses. It has been known for a long time that fluoride ion, optionally in combination with stannous ions, such as in the form of stannous fluoride, is beneficial in preventing erosive tooth demineralisation.
Chitosan has occasionally been used or studied in oral care. GB 2132889A describes oral care products containing chitin derivatives such as chitosan, and discloses that chitin or chitosan may act as a cure or prophylaxis in case of dental caries, periodontoclasia and halitosis, and that in a dentifrice chitosan salts may mask the taste of a silica abrasive. WO 02/17868A describes oral and dental hygiene agents containing chitosan microcapsules, the microcapsules being loaded with an active agent which may be, among others, stannous fluoride. Its compositions are said to have protective effect against caries, periodontosis and plaque, and to have anti-inflammatory effect. WO 03/042251A discloses compositions, such as oral care compositions, comprising chitosan in the form of nano-sized fibres and which also may contain a fluoride source. These compositions are said to improve general gum and teeth health, to be suitable for treatment of halitosis and gingivitis, to reduce staining of the teeth, to provide anti-caries, anti-plaque and anti-calculus benefits, to inhibit cariogenic bacteria, and to inhibit hydrogen sulphide and volatile odiferous organosulphide compounds produced by salivary microorganisms. For the chitosan itself it is stated that it has film-forming and pH-buffering capabilities. JP 2006/241122A discloses compositions, which may be oral care compositions, which comprise glucosamine and/or chitosan oligosaccharide, and a remineralisation promotion constituent containing a fluorine ion source. The “remineralisation” is in the case of carious lesions produced by streptococcus mutans. WO 2008/121518A discloses polymeric microcapsules, which may preferably be chitosan microcapsules, and which may be used in dentifrices which may contain a fluoride source. The capsules also contain a quaternary ammonium salt. The compositions are said to be antimicrobial. Recently a toothpaste called “Chitodent” has appeared on the German market. According to its advertisement it contains chitin, chitosan and silver ions, but is devoid of fluoride. Stamford Arnaud T M et al. J Dent 38 (2010)848-852 studied the remineralising effect of chitosan in human tooth samples which had been demineralized with acetate buffers of pH 4.0 and 4.8, which is a model for caries-related demineralization. Ganss C, Schlüter S. Quintessenz 61 (2010)1203-1210 discusses prospective new agents for the indication of erosive tooth demineralisation and mentions chitosan but states that “proof of activity so far is not available”. In a poster by Neutard et al. presented at the 57th congress of the European Organization for Caries Research (ORCA, Montpellier, France, July 2010), activities of some fluoride-containing toothpastes and some “special free fluoride-free toothpastes” (among which was the above mentioned Chitodent) in the prevention of erosive tooth demineralisation were determined. The authors concluded that “the fluoride-free preparations had no significant effect” and that “the special formulations were not superior or even less effective compared to conventional products”.
The present application seeks to provide new treatment and prevention routes against erosive tooth demineralisation caused by strong food acids or strong endogenous acids such as gastric juice.